Field of the Invention
The present invention relates to a multi-layer capacitor using a poling process for reduction of vibration, and more specifically, to a multi-layer capacitor which uses a dielectric substance poling-processed in advance to eliminate mechanical vibration generated by piezoelectric characteristics of the dielectric material of the multi-layer capacitor or noises generated by the vibration.
Background of the Related Art
A capacitor is a passive element performing a function of accumulating electric charges by applying voltage and according to thickness of a dielectric material and connection of electrodes, and a multi-layer capacitor is a chip type capacitor stacking multiple layers of dielectric materials and electrode areas in the form of small-sized thin films according to usage of electrostatic capacity and rated voltage. Particularly, a multi-layer ceramic capacitor, the dielectric material of which is configured of ceramic, is mainly used as the multi-layer capacitor.
Multi-layer ceramic capacitors are mainly used for TVs, VCRs, PCs, Automotive Electrical Components and communication devices since they have a low lead inductance and excellent high frequency properties. The multi-layer ceramic capacitors are ceaselessly developed in close connection with trends of set devices and, recently, they are developed further more rapidly owing to miniaturization of set devices focused on mobile communication devices. Electrostatic capacity of the multi-layer ceramic capacitors also increases owing to thin and multi-layered dielectric layers, expansion of effective areas, improvement of materials and the like.
Barium titanate of high permittivity and superior dielectric loss is used as a main matter (or compound) of the dielectric material of the multi-layer ceramic capacitors. However, the barium titanate has a disadvantage of a large piezoelectric coefficient. The piezoelectric coefficient generates vibration of an audible frequency band in a substrate, in which the multi-layer ceramic capacitor is installed, by converting electrical signals into mechanical signals. Such vibration lowers reliability of the installed parts or generates noises by generating vibration of a printed circuit board. When a voice communication is performed using a cellular phone, this vibration is output through a speaker as a noise.
Although a method of installing two multi-layer ceramic capacitors up and down has been proposed in the prior art to prevent vibration generated by the multi-layer ceramic capacitors or noises generated by the vibration, it works as a factor of design constraint of a printed circuit board, and if one of the two multi-layer ceramic capacitors is applied only to offset the vibration, there is a problem of lowering installation density of the printed circuit board.
In addition, also a method of eliminating vibration generated by the multi-layer ceramic capacitor or noises generated by the vibration by packaging a plurality of multi-layer ceramic capacitors using an insulative flexible substrate of 50 to 500 μm and absorbing the vibration generated by the multi-layer ceramic capacitors using the insulative flexible substrate or lead terminals has been proposed, there is a disadvantage in that it is practical only when the plurality of multi-layer ceramic capacitors is used as a package, and it can be used only exactly as the multi-layer ceramic capacitors are installed in advance.